A predetermined circuit pattern is formed on the surface of a wafer by utilizing a photoresist, after a high-purity single crystal semiconductor has been sliced in order to gain the wafer, and, then, the rear surface of the wafer is polished by means of a polishing machine so as to reduce the thickness of the wafer from approximately 100 to 600 μm and, finally, the wafer is diced so as to gain chips and, thereby, a conventional semiconductor integrated circuit (IC chip) is manufactured.
Here, at the time of the above-described polishing, an adhesive sheet or the like (tape for polishing) is adhered to the top surface of the wafer so that the wafer is prevented from being damaged and so that the polishing process is easily carried out, and at the time of the above-described dicing, an adhesive sheet or the like (dicing tape) is adhered to the rear surface of the wafer so that the wafer is diced in an adhered and secure condition, and the formed chips are picked by being pushed up by a needle from the film substrate side of the dicing tape and are secured to a die pad.
In recent years, as applications of IC chips have widened, an extremely thin wafer having a thickness of approximately 50 μm that can be used in an IC card or the like, or that can be utilized in a layered form has been in demand. However, the wafer having a thickness of approximately 50 μm greatly develops a warp and easily cracks due to impact as compared with that of a conventional wafer with a thickness of from approximately 100 to 600 μm and, therefore, in the case where a similar process for a conventional wafer is carried out, in the step of polishing which is easily suffered an impact, in the step of dicing and at the time when a bump is manufactured on an electrode of an IC chip, such a thin wafer easily becomes damaged, resulting in a poor yield. Therefore, improvement in the ease of handling of the wafer in the process wherein an IC chip is fabricated from a wafer having a thickness of approximately 50 μm has become an important issue to be solved.
In contrast to this, a method has been proposed wherein a wafer is adhered to a support plate via a support tape and polishing is carried out in securing to the support plate. Improvement in the strength and flatness of the wafer can be secured by the support plate and the ease of handling of the wafer can be improved according to this method.
However, there is a problem with this method, wherein a wafer having a thickness of approximately 50 μm is weak in structural strength and, therefore, damage or deformation occurs due to a load at the time when the wafer is removed from the support plate or the support tape. In addition, though extremely thin wafers having a thickness of approximately 50 μm can be laminated in greater numbers than conventional wafers having a thickness of from approximately 100 to 600 μm, there is a problem wherein such extremely thin wafers are required a higher level of flatness in order to laminate many layers.